1. Field of the Invention
The present invention generally relates to mounting of assembly of servers and other computer equipment, telecommunications equipment, and electronics in a standard enclosure or box (simply called “chassis” herein) that will then, often but not always, be mounted in a rack with other enclosures/boxes (i.e., each being a rack-mountable chassis), and, more particularly, to an mounting or fastening assembly adapted for positioning, attaching, and supporting a printed circuit board (PCB) or PCB with other electronic components in the form of a printed circuit assembly (PCA) (herein, both are referred to more simply as “boards”), with a typical arrangement being to mount the board vertically within a chassis between two vertical chassis sidewalls such as to provide a midplane board (or midplane PCA).
2. Relevant Background
There are numerous settings or environments where electronic equipment, computers and computer equipment (e.g., servers, routers, and so on), and telecommunications equipment are provided in a centralized location in standard or conventional racks. Often, this equipment is provided within a box or chassis that is then mounted within the rack. Such use of racks with configurable electronic or computer devices each in a chassis can be found in data centers, computer rooms, network rooms, control rooms, telecommunication centers, and so on.
As a specific example, servers and other computing devices are often each provided in such a chassis. During assembly of each of these devices, it is common for a PCB or PCA (or “board”) to be mounted vertically in each with its ends extending between the vertical side walls of the chassis. Such a board is mounted between the rear and front ends of the chassis, and this PCA or simply “board” or “circuit board” may be a midplane board (or midplane PCA). Assembly of a server or other device in a chassis can be time consuming and tool-intensive work, and this is due, in part, to the need for very accurate alignment of the midplane board within the chassis to allow later installed components to mate with the midplane boarder.
More specifically, the midplane board has to be provided in a specific location (as measured with X, Y, and Z coordinates) so that its connectors can be effectively mated with connectors on the later installed components (such as a fan module, a data storage module, a power module, and so on). In most designs, a bulkhead that was fabricated to be rigid and relatively heavy duty was provided in the chassis, with the bulkhead including a plurality of guide pins for receiving the midplane board. Assembly required attachment of the midplane board to this bulkhead with a plurality of fasteners to achieve desired alignment and support of the midplane board. This design required a larger number of parts and tools such that it was relatively costly with regard to parts and/or materials and with regard to assembly time (i.e., some assembly times are in the range of 25 to 35 minutes for midplane board installation in a chassis).
In designing chassis-based computer and other devices, mechanical tolerance stacks can make it difficult to achieve full connector mate, and achieving proper midplane board-to-inserted module/component connection can be especially problematic on blind-mate assemblies and even more so when sequencing of connections exist in the device's design. For example, on an edge card connector, there may be three or more sequential mates, which requires that the pads on the midplane board be increasingly shorter lengths and, yet, all must be fully engaged electrically with the mating connector when the assemblies are fully seated. Consequently, the tolerance margin for full mate becomes increasingly small, and this leads to issues including over-mate (i.e., parts crashing together during assembly or assemblies not being able to properly install and/or latch) or under-mate (i.e., one or more electrical connections with insufficient contact leading to improper operations of the assembled device).
One way that industry designers have addressed these assembly challenges is to have mechanical compliance designed into one or more assemblies. For example, a design may include floating connectors and floating boards, which are designed with a spring force and a nominal over-mate. In other designs, there are ejector arms, which use cam action to seat the connector and allow some over-mate while allowing the overall system compliance (e.g., chassis parts, midplane board bending, and the like) to act as the “spring.” In many existing designs, the midplane board must be seated accurately to reduce the tolerances between the mating connectors. To this end, a large, expensive machined bulkhead is employed in the design, and the midplane board is fastened to this bulkhead with screws. However, accessing these screws with a screw driver is often difficult because the midplane board is buried in the middle of the chassis, which can cause assembly issues or, at the very least, undesirably increase the assembly time required for such designs.